In a general aircraft, an aerodynamic device such as an elevator and a spoiler is used for adjusting a path angle at the time of descent so that an airframe is not deviated from a desirable path.
The aerodynamic device may change both of the path angle and an airspeed.
For example, as shown in FIG. 29, the aerodynamic device normally has to proceed at the path angle shown by a solid line. When the airspeed is operated by the aerodynamic device, the path angle is changed. Actually, other operations for repeatedly modifying the path angle may result in a path shown by a dotted line.
Accordingly, the operation tends to be complex. In addition, once gusty wind attacks the aerodynamic device, workloads of a pilot significantly increase, thereby causing safety issues.
This is because an existing aerodynamic device changes not only a drag force but also a lift force of the airframe and the path angle or the descending rate cannot be controlled directly.
On the other hand, in an electrified aircraft having a propulsion drive system driven by an electric drive motor, it is possible to use the propeller or the fan not only for propulsion but also for generating an electric power (see Patent Document 1). At the time, the drag force opposite to the drive force at the time of propulsion is generated at the propeller or the fan.
Patent Document 1: Japanese Patent No. 3942570